27th Symposium on Photonics and Optics (SPO 2026)

Is Landau Potential Picture Useful for Photoinduced Phase Transitions?

Mo2.1

2 Nov 2026, 11:25

40m

Online (Zoom)

Invited Talk Ultrafast Phenomena Workshop on Ultrafast Phenomena

Speaker

Hervé Cailleau (Institut de Physique de Rennes, University of Rennes and CNRS, France)

Description

Thanks to remarkable developments of ultrafast techniques operating on a few fs, i.e. faster than atomic motions, many functionalities of materials can be manipulated on demand in unprecedented ways [1]. Thus, ultrafast laser systems allow to photoexcite a macroscopic number of carriers (typically few percent of valence band electrons) and hence to strongly perturb the electronic state of materials to drive the system toward another phase. The resulting electronic, magnetic and/or structural reorganization can be probed in real-time by ultrafast spectroscopies and X-ray/electron scattering.

Thermodynamics and symmetry considerations offer an universal approach of phase transition at thermal equilibrium through the Landau potential picture. A fundamental question arises whether it is applicable to ultrafast photoinduced phase transitions.

Different essential points will be discussed in views of recent ultrafast experiments:

• symmetry breaking (instability) vs. isosymmetric (switching) phase transitions;
• from short-range interactions in fluid to infinite-range ones in elastic solid;
• laser pulse vs. thermostat energy deposit;
• displacive dynamics for structural symmetry breaking [2];
• volume strain dynamics driving isosymmetric transformations in solids [3,4];
• influence of material morphology on transformation dynamics;
• comparison with nonlinear bistable systems like neuromorphic ones.

References

[1] D.N. Basov et al., Towards properties on demand in quantum materials, Nature Materials 16, 1077 (2017).
[2] T. Huber et al., Coherent structural dynamics of a prototypical charge-density-wave-to-metal transition, Physical Review Letters 113, 026401 (2014).
[3] C. Mariette et al., Strain wave pathway to semiconductor-to-metal transition revealed by time-resolved X-ray powder diffraction, Nature Communications 12, 1239 (2021).
[4] T. Amano et al., Propagation of insulator-to-metal transition driven by photoinduced strain waves in a Mott Material, Nature Physics 20, 1778 (2024).